This invention relates, in general, to fluid heater apparatus and, more particularly, to fluid heater apparatus which provides a heated wash fluid to a cleanable surface, and, still more specifically, to a heated wash fluid apparatus for a vehicle windshield wash system.
It is necessary in many diverse applications to quickly elevate the temperature of a fluid to a higher use temperature. For example, it is desirable to be able to provide instant hot water, for use in homes, offices and campers, as well as for industrial processes.
In cleaning applications, it is known that hot fluid removes dirt and other debris from a surface much better and much faster than colder fluids. One heated fluid application is a vehicle wash fluid system, such as a windshield wash system as well as vehicle wash systems applied to camera lenses, exterior lamps and lamp lenses, mirrors, etc. Vehicles are typically provided with at least one and usually multiple windshield washers which are used to clear the field of vision in a windshield or rear backlight.
Typically, a nozzle or spray device is provided adjacently to or as part of the windshield wiper to disperse a pattern of wash fluid onto the windshield prior to and during the wiping operation to improve the efficiency of the wiping operation so as to provide a clear field of vision for the driver or vehicle passengers. The wash fluid is typically stored in a reservoir in the engine compartment and is pumped through the spray device upon manual activation of a control actuator by the vehicle driver.
Since it is known that warm or heated fluid provides better cleaning efficiency than cold fluid, it is also known to provide a heated wash fluid to a vehicle window spray device. Conventional thought would be that the higher the temperature, the better the cleaning results. However, this may not be the case, since the presence of certain elevated fluid temperature levels may create significant problems.
Safety to humans is paramount in all product designs. It is believed that fluid temperatures in excess of 70° C. can cause significant skin damage with very limited exposure. Therefore, while a fluid temperature profile higher than 70° C. may be beneficial for cleaning and defrost performance, it is counterproductive for the safety of the human user.
Protection of other devices and/or fluid wash components is also a consideration. Many components in a vehicle fluid washer system and other components on the vehicle that may be exposed to the fluid from the washer system are made of materials that may be damaged by fluid temperatures that may exceed 70° C. Again, while cleaning performance at these temperature levels may be improved, it would be inappropriate to damage the washer system and other vehicle components and subsystems, such as hoses, hose fittings, check valves, blades, glass surfaces and, particularly, glass surfaces with cracks or chips, etc.
In addition, windshield washer fluid is often made up of volatile fluids, the most common of which is alcohol. Alcohol in a water mixture is relatively safe except when the temperature is high enough to boil the alcohol from the solution. If the fluid temperature reaches the boiling point, the alcohol can be driven from the solution, which greatly diminishes the effectiveness of the washer solution at lower temperatures. In addition, if the temperature is too high, it may actually result in a flash condition with the gaseous alcohol.
Windshield washer fluid also may contain detergent or other additives that may be sensitive to temperature. Elevated temperatures tend to cause some detergents to precipitate, with both situations being negative to the effectiveness of the washer fluid. Such conditions may also result in damage to downstream components since as washer nozzles by causing the washer nozzles to clog or be restricted by glycerin or paraffin residues. Some washer fluids now contain acrylic material which, after exposure to elevated temperatures above approximately 70° C., may cause the acrylic material to cure and plug the nozzle.
In many areas, consumers may use water exclusively or, in the case of European markets, tap water which is mixed with alcohol to create a windshield washer solution. In areas of very hard water, this can present a problem in a heated environment. While many factors contribute to the detrimental formations of calcium plaque, temperature is a key one. In elevated temperatures, this can generate a problem. The potential problem is exasperated by the function of the washer system as it operates. A pump pressurizes the system to push fluid through the delivery lines to a restrictive orifice at the nozzle. This can cause otherwise benign suspended colloidal calcium to impact and stick to the nozzles. In time, this can result in the nozzle becoming plugged.
Thus, it would be desirable to provide a fluid heater apparatus which provides a heated fluid control apparatus for maintaining the temperature of a cleaning fluid at an optimum efficiency level; while at the same time at a temperature level which is below threshold temperatures that could cause damage to the human user, etc.